Compliant bonding structures for semiconductor devices

ABSTRACT

A compliant bonding structure is disposed between a semiconductor light emitting device and a mount. When the semiconductor light emitting device is attached to the mount, for example by providing pressure, heat, and/or ultrasonic energy to the semiconductor light emitting device, the compliant bonding structure collapses to partially fill a space between the semiconductor light emitting device and the mount. In some embodiments, the compliant bonding structure is plurality of metal bumps that undergo plastic deformation during bonding. In some embodiments, the compliant bonding structure is a porous metal layer.

FIELD OF INVENTION

The invention relates to the field of bonding semiconductor devices toother structures, and more specifically to compliant bonding structuresfor mounting semiconductor light emitting devices on other structures.

BACKGROUND

Semiconductor light-emitting devices including light emitting diodes(LEDs), resonant cavity light emitting diodes (RCLEDs), vertical cavitylaser diodes (VCSELs), and edge emitting lasers are among the mostefficient light sources currently available. Materials systems currentlyof interest in the manufacture of high-brightness light emitting devicescapable of operation across the visible spectrum include Group III-Vsemiconductors, particularly binary, ternary, and quaternary alloys ofgallium, aluminum, indium, and nitrogen, also referred to as III-nitridematerials. Typically, III-nitride light emitting devices are fabricatedby epitaxially growing a stack of semiconductor layers of differentcompositions and dopant concentrations on a sapphire, silicon carbide,III-nitride, composite, or other suitable substrate by metal-organicchemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), orother epitaxial techniques. The stack often includes one or more n-typelayers doped with, for example, Si, formed over the substrate, one ormore light emitting layers in an active region formed over the n-typelayer or layers, and one or more p-type layers doped with, for example,Mg, formed over the active region. Electrical contacts are formed on then- and p-type regions.

US Patent Application 2007-0096130 describes “a process for forming anLED structure using a laser lift-off process to remove the growthsubstrate (e.g., sapphire) after the LED die is bonded to a submount. Toobviate the need to use an underfill between the submount and the LEDdie to support the die, the underside of the LED die has formed on itanode and cathode electrodes that are substantially in the same plane,where the electrodes cover at least 85% of the back surface of the LEDstructure. The submount has a corresponding layout of anode and cathodeelectrodes substantially in the same plane.

“The LED die electrodes and submount electrodes are interconnectedtogether such that virtually the entire surface of the LED die issupported by the electrodes and submount. No underfill is used.Different methods for LED to submount interconnection can be used, suchas ultrasonic or thermosonic metal-to-metal interdiffusion (Gold-Gold,Copper-Copper, other ductile metals, or a combination of the above), orsoldering with different alloy compositions such as Gold-Tin,Gold-Germanium, Tin-Silver, Tin-Lead, or other similar alloy systems.

“The growth substrate, forming the top of the LED structure, is thenremoved from the LED layers using a laser lift-off process, whichablates the material at the interface of the growth substrate and theLED layers. The extremely high pressures created during the laserlift-off process do not damage the LED layers due to the large areasupport of the LED layers by the electrodes and submount. Othersubstrate removal processes can also be used.

SUMMARY

An object of the invention is to provide an electrical, mechanical, andthermal connection between a semiconductor light emitting device and astructure on which the semiconductor light emitting device is mounted.

In accordance with embodiments of the invention, a bonding structure isdisposed between a light emitting device and a mount. In an areaunderlying a small area contact of the light emitting device, thebonding structure comprises a plurality of metal regions separated bygaps. Nearest neighbor metal regions are separated by a gap less than 5microns wide. In some embodiments, the metal regions comprise gold bumpscompressed by bonding the light emitting device to the mount.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross section of a III-nitride device grown on a substrate.

FIG. 2 is a cross section of the device of FIG. 1 after depositing andpatterning a photoresist layer.

FIG. 3 is a cross section of the device of FIG. 2 after depositing metalin the openings in the photoresist layer.

FIG. 4 is a cross section of the device of FIG. 3 after stripping thephotoresist layer.

FIG. 5 is a cross section of the structure of FIG. 4 connected to amount.

FIG. 6 is a cross section of a III-nitride device connected to a mount.

FIG. 7 is a plan view of an LED device with microbumps and an edge seal.

FIG. 8 illustrates a continuous, linear edge seal.

FIG. 9 illustrates the edge seal of FIG. 8 after undergoing plasticdeformation during bonding.

FIG. 10 illustrates a continuous non-linear edge seal.

FIG. 11 illustrates the edge seal of FIG. 10 after undergoing plasticdeformation during bonding.

FIG. 12 illustrates a non-continuous edge seal.

FIG. 13 illustrates the edge seal of FIG. 12 after undergoing plasticdeformation during bonding.

FIG. 14 is a plan view of an LED device including a compliant bondingstructure according to embodiments of the invention.

FIG. 15 is a cross section of the device illustrated in FIG. 14.

FIG. 16 is a plan view of a mount on which the device illustrated inFIG. 14 may be mounted.

FIG. 17 is a cross section of the mount illustrated in FIG. 16.

FIG. 18 is a plan view of an LED device including a compliant bondingstructure according to embodiments of the invention.

FIG. 19 is a plan view of a mount on which two of the devicesillustrated in FIG. 18 may be mounted.

DETAILED DESCRIPTION

In devices with large-area metal contacts, as described above in USPatent Application 2007-0096130, large bonding pressure and ultrasonicpower may be necessary during bonding, to overcome slight variations inthe topography of the LED die electrodes and the submount electrodes.Aggressive bonding conditions can cause damage to the semiconductormaterial in the LED during bonding. Aggressive bonding conditions may benecessitated by the lack of compliance (i.e. deformation and collapse)in the electrodes during bonding, due to the large area of theelectrodes.

In some embodiments of the invention, a compliant bonding structure isdisposed between an LED die and a mount. The compliant bonding structuremay be disposed on the LED die, on the mount, or on both the LED die andthe mount. During bonding, the compliant structure collapses andreflows, resulting in a robust electrical, thermal, and mechanicalconnection that may not require aggressive bonding conditions and thatmay compensate for slight variations in the topography of the LED dieand the mount.

FIGS. 1-4 illustrate how to form a compliant bonding structure accordingto embodiments of the invention.

FIG. 1 illustrates a III-nitride device grown on a substrate 10.Substrate 10 may be any suitable growth substrate, including, forexample, sapphire, SiC, GaN, or engineered substrates such as SiCattached to an insulator, or III-nitride materials attached to aninsulator. Engineered substrates suitable for growth of III-nitridedevices are described in more detail in US Published Application2007-0072324, which is incorporated herein by reference.

An n-type region 12 is grown first over substrate 10. N-type region 12may include multiple layers of different compositions and dopantconcentration including, for example, preparation layers such as bufferlayers or nucleation layers, which may be n-type or not intentionallydoped, release layers designed to facilitate later release of the growthsubstrate or thinning of the semiconductor structure after substrateremoval, and n- or even p-type device layers designed for particularoptical or electrical properties desirable for the light emitting regionto efficiently emit light.

A light emitting or active region 14 is grown over n-type region 12.Examples of suitable light emitting regions include a single thick orthin light emitting layer, or a multiple quantum well light emittingregion including multiple thin or thick quantum well light emittinglayers separated by barrier layers. For example, a multiple quantum welllight emitting region may include multiple light emitting layers, eachwith a thickness of 25 Å or less, separated by barriers, each with athickness of 100 Å or less. In some embodiments, the thickness of eachof the light emitting layers in the device is thicker than 50 Å.

A p-type region 16 is grown over light emitting region 14. Like then-type region, the p-type region may include multiple layers ofdifferent composition, thickness, and dopant concentration, includinglayers that are not intentionally doped, or n-type layers.

In some embodiments, substrate 10 is about 90 microns thick, and thedevice layers 12, 14, and 16 have a combined thickness less than 5microns.

After growth of semiconductor regions 12, 14, and 16, one or moreportions of p-type region 16 and light emitting region 14 are etchedaway to reveal portions of n-type region 12. An n-contact 26 is formedon the exposed portions of n-type region 12.

A multi-layer p-contact is formed over p-type region 16. In the exampleshown in FIG. 1, an ohmic contact layer 18 is formed in direct contactwith p-type region 16, then a guard layer 20, which may be metal ordielectric, is formed over ohmic contact layer 18. As illustrated inFIG. 1, guard layer 20 may extend over the sides of ohmic contact layer18. For example, ohmic contact layer 18 may include silver, which issubject to electromigration which can cause shorting or reliabilityproblems. Guard layer 20, formed over ohmic contact layer 18, mayprevent or reduce electromigration of ohmic contact layer 18. In someembodiments, more p-contact layers may be used, or guard layer 20 may beomitted.

A dielectric layer 22 may isolate n-contact 26 from the p-contact 18,20.

A p-bond pad 24 is formed over and electrically connected to thep-contact. An n-bond pad 28 is formed over and electrically connected tothe n-contact. Bond pads 24 and 28 support the device layers 12, 14, and16 during removal of growth substrate 10, and conduct heat away from thedevice layers. Bond pads 24 and 28 may be formed from any metal withhigh thermal conductivity, such as, for example, gold, copper, oraluminum. Bond pads may be, for example, electroplated to a thicknessbetween 6 and 30 microns in some embodiments, between 15 and 25 micronsin some embodiments. Air gaps 30 may electrically isolate n- and p-bondpads 28 and 24, as illustrated in FIG. 1. The gaps are preferably lessthan 50 microns wide. As described above, bond pads 24 and 28 provideheat transfer and support the semiconductor layers during removal ofgrowth substrate 10. In devices that do not require the heat transferprovided by bond pads 24 and 28 and that do not require support of thesemiconductor layers (i.e., in devices where the growth substrate is notremoved from the device), bond pads 24 and 28 may be omitted, andmicrobumps 32 may be formed directly on the p- and n-contacts.

N- and p-bond pads 28 and 24 cover at least 60% of the area of the LED(i.e., the area of semiconductor material on the LED) in someembodiments, at least 85% of the area of the LED in some embodiments.

Details of steps that may be conventional or well known in the art offorming III-N LEDs do not need to be described, and there may be manyways of forming the same structure shown in the figures. Such detailsthat may be conventional or well known include cleaning, depositiontechniques (e.g., sputtering, CVD, electro-plating, etc.), lithographictechniques, masking techniques, etching techniques, metal lift-offtechniques, photoresist stripping techniques, and separating dice from awafer.

In FIG. 2, a photoresist layer 34 is formed over the top of p-bond pad24 and n-bond pad 28, then patterned to form a series of small openings.

In FIG. 3, a compliant metal 32 is electroplated in the openings inphotoresist layer 34. Any suitable metal, for example with a Young'smodulus less than 150 GPa, may be used. Examples of suitable metalsinclude gold, with a Young's modulus of about 78 GPa, copper, with aYoung's modulus between about 110 and 128 GPa, and aluminum, with aYoung's modulus of about 70 GPa.

In FIG. 4, the photoresist layer 34 is stripped, leaving compliant metalmicrobumps 32. Microbumps 32 may be, for example, between 6 and 25microns in lateral extent. They may have a circular cross section,though any cross section that can be patterned in photoresist layer 34may be used. Microbumps may be between 6 and 25 microns tall, and spacedbetween 6 and 25 microns apart. Microbumps may have approximately thesame height and width. In some embodiments, the size, height, andspacing of microbumps 32 are determined by the thickness of photoresistlayer 34. The spaces in photoresist layer 34 in which microbumps 32 areplated can be made about as wide and spaced about as far apart as thephotoresist layer is thick. For example, if a 10 micron thickphotoresist layer is used, the smallest microbumps patterned may beabout 10 microns wide and spaced about 10 microns apart. In someembodiments, the size, height, and spacing of microbumps 32 areunrelated to the thickness of photoresist layer 34. The microbumps canbe made thicker than photoresist layer 34, though mushroom heads willform above the photoresist layer. The size and spacing of microbumps 32are selected such that when the LED die is attached to a mount, themicrobumps deform such most or all of the area between the LED die andthe mount is filled with microbump material, leaving very small or nogaps between the LED die and the mount. For example, after attaching theLED die to a mount, in an area where the microbumps are formed (forexample, the area of n- and p-bond pads in some embodiments) the spacebetween the LED die and the mount is at least 50% filled with deformedmicrobumps in some embodiments, at least 75% filled with deformedmicrobumps in some embodiments, and at least 85% filled with deformedmicrobumps in some embodiments. The gaps between adjacent microbumpsafter bonding may be less than 5 microns in some embodiments, less than2 microns in some embodiments, and less than 1 micron in someembodiments. The height of microbumps after bonding may be less than 50%the original height in some embodiments, less than 20% the originalheight in some embodiments, and less than 10% of the original height insome embodiments.

After the processing illustrated in FIG. 4, a wafer of devices may bediced.

In FIG. 5, the device illustrated in FIG. 4 is flipped and mounted on amount 40. Microbumps 42 may be formed on mount 40 to align withmicrobumps 32 formed on LED die 5. Microbumps may be formed on only oneof LED die 5 and mount 40, or on both. LED die 5 is connected to mount40 by applying pressure between LED die 5 and mount 40. Pressure may beaccompanied by ultrasonic energy, heat, or both. The addition of one orboth of ultrasonic energy and heat may reduce the pressure necessary toform a bond. Microbumps 42 formed on the mount and/or microbumps 32formed on the LED die undergo plastic deformation (i.e., they do notreturn to their original shape) during bonding and form a continuous ornearly continuous metal support between the LED die and mount 40. Forexample, in some embodiments, after bonding, microbumps fill nearly allthe space between the LED die and mount 40 corresponding to an area ofn- and p-bond pads 28 and 24.

During ultrasonic bonding, LED die 5 is positioned on mount 40. A bondhead is positioned on the top surface of LED die 5, often the topsurface of sapphire growth substrate 10 in the case of a III-nitridedevice grown on sapphire. The bond head is connected to an ultrasonictransducer. The ultrasonic transducer may be, for example, a stack oflead zirconate titanate (PZT) layers. When a voltage is applied to thetransducer at a frequency that causes the system to resonateharmonically (often a frequency on the order of tens or hundreds ofkHz), the transducer begins to vibrate, which in turn causes the bondhead and LED die 5 to vibrate, often at an amplitude on the order ofmicrons. The vibration causes atoms in the metal lattice of microbumps32 and 42 to interdiffuse, resulting in a metallurgically continuousjoint. Heat and/or pressure may be added during bonding. Duringultrasonic bonding, compliant bonding structures such as microbumps 32and 42 collapse and reflow.

In some embodiments, the characteristics or arrangement of microbumpslocated at different parts of the device may have different properties.For example, microbumps may be larger and/or spaced more closelytogether in areas of the device that need more support during substrateremoval. For example, in the areas near where the mesas are etched toexpose the n-type region, the remaining p-type material may be thinnedslightly, due to the mesa etch. In these areas, microbumps may be largerand/or more closely spaced, to provide more support to the thinnersemiconductor material.

Microbumps 32 may be formed by other techniques, such as, for example,using a photoresist mask and a metal lift-off method, or by mechanicallypatterning a deposited or plated large-area, thick bonding pad.Mechanical patterning techniques include, for example, stamping, lasermachining, chemical or dry etching, or mechanical roughening. In someembodiments, multiple, stacked layers of microbumps which are offsetfrom each other may be used. Multiple layers of microbumps may result inbonding compliance in both lateral and vertical directions.

In some embodiments, microbumps 32 and 42 are replaced with a differentcompliant, electrically, and thermally conductive structure. FIG. 6illustrates an example of an alternate embodiment. Instead ofmicrobumps, a porous metal structure 46 is disposed between LED die 5and mount 40. Porous metal structure 46 may be formed on bond pads 24and 28 of LED die 5, on bond pads 44 of mount 40, or on both the LEDbond pads and the mount bond pads. Porous metal structure 46 may beformed by, for example, plating a soft metal under process conditionsthat made the plated surface porous, rough, or dendritic in nature, orby sintering small particles of metal to make a fused porous structure.LED die 5 and mount 40 may then be bonded as described above. Porousmetal structure 46 may undergo plastic deformation during bonding.Unlike solder, which becomes liquid during bonding, compliant bondingstructures such as the microbumps and porous metal structures describedherein generally collapse in the solid phase. Though heat may be appliedduring bonding which may cause the compliant bonding structure to becomesofter or to begin to melt, in some embodiments the compliant bondingstructure does not get hot enough to become completely liquid phase.

A compliant structure such as microbumps or a porous metal structure maycompensate for slight surface non-planarities between the bond pads onthe LED die and the surface of the mount on which the LED die ismounted, without requiring high pressure or temperature during bonding.The ability of microbumps to deform may reduce the pressure and/ortemperature required to form a bond with robust thermal, mechanical, andelectrical connections, and may reduce the occurrence of cracking orother damage during bonding to the mount.

After bonding LED die 5 to mount 40, growth substrate 10 may be removed,for example by laser lift off, etching, or any other technique suitableto a particular growth substrate. After removing the growth substrate,the semiconductor structure may be thinned, for example byphotoelectrochemical etching, and/or the surface may be roughened orpatterned, for example with a photonic crystal structure. A lens,wavelength converting material, or other structure known in the art maybe disposed over LED 5 after substrate removal.

In some embodiments, the microbumps along the edge of LED die 5 areconfigured to form a seal during bonding. In the device illustrated inFIG. 4, microbumps 50 on the edge of the device are configured to form aseal. The seal may provide extra mechanical support to the edge of thedevice and may prevent foreign material such as humidity or siliconeencapsulants from entering any spaces between LED die 5 and mount 40.

FIG. 7 is a plan view of a device with a first example of an edge seal.In the device illustrated in FIG. 7, a continuous, linear bump seal 50surrounds microbumps 32. For example, an edge seal surrounds themicrobumps in p-bond pad area 24 at the edge of die 5 and surrounds agap 30 between the p-bond pad and the n-bond pad. Another seal surroundsthe microbumps formed on the n-bond pad area 28. FIG. 8 illustrates aportion of a device with a linear perimeter bump seal 50 a asillustrated in FIG. 7. Only a portion of linear bump seal 50 a is shown,and microbumps 32 are omitted for clarity. When pressure 52 is appliedto bump seal 50 a, such as while bonding device 5 to a mount (not shownin FIG. 8), bump seal 50 a can deform in only one direction, indicatedby arrows 54. FIG. 9 illustrates the edge seal of FIG. 8 afterundergoing plastic deformation during bonding. Edge seal 50 b has spreadout in the direction 54 indicated in FIG. 8.

Since the continuous linear edge seal 50 a illustrated in FIGS. 7 and 8can only deform in one direction, it is less compliant than microbumps32, which can deform in more than one direction. As a result, duringbonding, more force may be exerted on the portion of the LED deviceunderlying edge seal 50 a than is exerted on the portion of the LEDdevice underlying microbumps 32.

In some embodiments, an edge seal 50 is configured to deform in morethan one direction during bonding. In some embodiments, the shape ofedge seal 50 is selected such that the compliance of edge seal 50matches the compliance of microbumps 32.

FIG. 10 illustrates a portion of a device with an edge seal 50 c thatcan deform in more than one direction. Edge seal 50 c is a continuous,non-linear bump seal that surrounds microbumps 32. Only a portion ofseal 50 c is shown, and microbumps 32 are omitted for clarity. Edge seal50 c has a wavy shape. When pressure 52 is applied to bump seal 50 c,such as while bonding device 5 to a mount (not shown in FIG. 10), bumpseal 50 c can deform in more than one direction, indicated by arrows 55and 56. FIG. 11 illustrates the edge seal of FIG. 10 after undergoingplastic deformation during bonding. Edge seal 50 d has spread out in thedirections 55 and 56 indicated in FIG. 10.

FIG. 12 illustrates a portion of a device with another example of anedge seal 50 e that can deform in more than one direction. Edge seal 50e is two lines 50 f and 50 g of offset microbumps that surroundmicrobumps 32. Only a portion of edge seal 50 e is shown, and microbumps32 are omitted for clarity. Microbumps in lines 50 f and 50 g need notbe in contact with each other, though they may be. When pressure 52 isapplied to bump seal 50 e, such as while bonding device 5 to a mount(not shown in FIG. 12), bump seal 50 e can deform in more than onedirection, indicated by arrows 55 and 56. FIG. 13 illustrates the edgeseal of FIG. 12 after undergoing plastic deformation during bonding. Thetwo lines 50 f and 50 g of microbumps in edge seal 50 e have spread outin the directions 55 and 56 indicated in FIG. 12 to form a continuousseal 50 h.

During ultrasonic bonding, described above, the transducer generallyvibrates in a single direction. For example, the transducer may vibratealong axis 56, illustrated in FIGS. 10 and 12, and create little or nomotion along axis 55. Compliant bonding structures tend topreferentially collapse along the vibration axis. Accordingly, in someembodiments, edge seal 50 is wider along axes perpendicular to thevibration axis, and narrower along axes parallel to the vibration axis.

FIGS. 14-19 illustrate examples of LEDs and mounts. The LEDs describedbelow may be attached to the mounts by microbumps between the mount andone or both of n- and p-contacts. The LEDs described below have onelarge area contact and one small area contact. In some embodiments, thelarge area contact, often the p-contact, may be connected to the mountby conventional gold-gold interconnects or stud bumps, and the smallarea contact, often the n-contact, may be connected to the mount bymicrobumps, as described above. In contrast to the microbumps describedabove, conventional gold-gold interconnects are generally at least 25microns wide and spaced on the order of 100 microns apart.

FIG. 14 is a plan view of an LED die 5. FIG. 15 is a cross sectionalview of the device illustrated in FIG. 14, taken along axis 60.P-contact 62 may be, for example, a reflective layer, such as silver ora combination of silver and indium tin oxide, formed in direct contactwith p-type region 16. An evaporable, etchable barrier such as nickel,nickel vanadium, or palladium may be formed over the reflective layer.After depositing the p-contact metals 62, trench 68 is patterned, thenetched.

An n-contact 26 is formed in trench 68. N-contact 26 includes one ormore relatively narrow arms 64. In the device shown in FIG. 14, the fourarms in the n-contact are formed in an X-shape; however, the number andparticular arrangement of the arms may differ. In some embodiments,n-contact arms 64 extend to the edge of LED die 5, and/or may be formedon the periphery of LED die 5, surrounding the p-contact, if moren-contact area is required. The n-contact arms 64 may be tens of micronswide; for example, between 15 and 25 microns wide. The n-contact arms 64are formed in a trench 66 between, for example, 25 and 35 microns wide.The center section of the n-contact, shown by microbump area 32 b inFIG. 14, may be, for example, between 35 and 45 microns wide. The heightof the n-contact may be selected to be within a half micron of co-planarwith the top of p-type region 16, a height of a few microns in someembodiments. In some embodiments, when viewed as illustrated in FIG. 14,the top of the n-contact is below the top of the p-contact.

After the n-contact 26 is formed, a dielectric layer 22, such as SiN_(x)formed by plasma-enhanced chemical vapor deposition or AlO_(x) formed byelectron beam evaporation, is deposited to electrically isolate the n-and p-contacts. In some embodiments, a lower index of refractiondielectric layer may be used to reduce the amount of light leakingthrough dielectric layer 22. The dielectric layer is then etched back toexpose the p- and n-contacts, except for a 5 micron thick band 22 a onthe edges of the contacts, which is left to compensate for manufacturingtolerances. In conventional devices with small n-contact areas such asn-contact arms, the n- and p-contacts are typically redistributed tolarge-area contacts by a metal-dielectric layer stack. Any breach in thedielectric layer or layers in the stack can cause shorting, which maylead to device failure. In addition, forming the metal-dielectric layerstack requires additional lithographic steps. The use of microbumps, asdescribed below, may eliminate the requirement of redistributing thecontacts to large-area contacts. Dielectric layer 22 may be thin, forexample no thicker than 0.5 microns in some embodiments, no thicker than0.4 microns in some embodiments. The use of microbumps, as describedbelow, may also eliminate the need to use underfill to support the dieduring substrate removal, though underfill may be used in someembodiments, for example to supplement the support provided by themicrobumps and other interconnects, or to provide a seal to preventhumidity or other contaminants from inhabiting the space between the LEDand the mount.

Microbumps 32 are then formed on n- and p-contacts 26 and 62. Microbumps32 b are formed on the p-contact 62, and microbumps 32 a are formed onn-contact 26. Microbumps 32 a are limited to the center section of then-contact 26; no microbumps are formed on n-contact arms 64. The centersection of the n-contact on which the microbumps are formed need not bein the center of the device, as shown in FIG. 14. N-contact arms 64 donot contact mount 40, since they are recessed relative to the height ofmicrobumps 32 a and 32 b. The compliance of microbumps 32 compensatesfor any variation in height between dielectric layer 22 a, the top ofn-contact 26, and the top of p-contact 62.

In some embodiments, to prevent damage to the semiconductor layersduring removal of the growth substrate, the gaps between regions withmicrobumps are limited to less than 40 microns. For example, thetrenches 66 in which n-contact arms 64 are formed are limited to lessthan 40 microns, and the gap 67 between microbump regions 32 a and 32 bshown in FIG. 15 is limited to less than 40 microns in some embodiments,and less than 20 microns in some embodiments. In some embodiments,electrically isolated microbumps may be formed in the areas between then- and p-contact microbumps 32 a and 32 b. Such microbumps support thedevice during substrate removal, but are electrically isolated, forexample by a dielectric layer.

FIG. 16 is a plan view of a mount 40 on which the device shown in FIGS.14 and 15 may be mounted. FIG. 17 is a cross sectional view of the mountof FIG. 16 taken along axis 78. Mount 40 includes a body 70, which maybe an insulating material such as ceramic, or a semiconducting materialsuch as silicon. N-bond pad 72 a aligns with the microbumps 32 aelectrically connected to the n-contact 26 on LED die 5, as illustratedin FIG. 15. P-bond pad 72 b aligns with the microbumps 32 b electricallyconnected to the p-contact 62 on LED die 5. The gap 76 between n-bondpad 72 a and p-bond pad 72 b may be, for example, at least 15 micronswide. Microbumps formed on mount 40 which align with microbumps 32formed on the LED die 5 may be formed on the n- and p-bond pads 72 a and72 b on mount 40. These microbumps are not shown in FIGS. 16 and 17. Ifaligning microbumps are formed on mount 40, obviously no aligningmicrobumps are formed on the mount areas corresponding to n-contact arms64. Vias 73 connect the n- and p-bond pads 72 a and 72 b on the top sideof body 70 to bottom side n- and p-bond pads 75 and 74.

FIG. 18 is a plan view of an LED die 5. FIG. 19 is a plan view of amount on which two LED dice may be mounted in series. Like the deviceillustrated in FIG. 14, in the device illustrated in FIG. 18, then-contact includes a center area on which microbumps 32 a are formed,and arms 64, on which no microbumps are formed. On the p-contact,microbumps 32 b are omitted from a gap 80, which may be, for example,between 25 and 40 microns wide.

Two LED dice may be mounted on the mount illustrated in FIG. 19, inareas 82 a and 82 b. The two devices are connected in series. A metaltrace 84 connects the n-contact region 72 a on device 82 a to thep-contact region 72 b on device 82 b. The devices on mount 40 may beelectrically connected to other structures (such as a circuit board) byn- and p-contact pads 86 and 85. Gap 80 in microbumps 32 b on the LEDdie shown in FIG. 18 is aligned with metal trace 84. Trace 84 may berecessed relative to the height of the microbumps 32 b surrounding gap80, such that trace 84 does not contact the p-contact on the die mountedover it.

Though the above-described examples and embodiments refer to flip clipIII-nitride light emitting devices, the compliant bonding structures andedge seals described herein may be used with any suitable device, whichneed not be a flip chip, a III-nitride device, an LED, or even a lightemitting device.

Having described the invention in detail, those skilled in the art willappreciate that, given the present disclosure, modifications may be madeto the invention without departing from the spirit of the inventiveconcept described herein. Therefore, it is not intended that the scopeof the invention be limited to the specific embodiments illustrated anddescribed.

1. A structure comprising: a light emitting device comprising: asemiconductor structure comprising a light emitting layer disposedbetween an n-type region and a p-type region; a metal p-contact disposedon the p-type region; and a metal n-contact disposed on the n-typeregion; wherein: the metal p-contact and the metal n-contact are bothformed on a same side of the semiconductor structure; and one of themetal p-contact and the metal n-contact is a large area contact and theother of the metal p-contact and the metal n-contact is a small areacontact, the large area contact having a larger area than the small areacontact; a mount; and a bonding structure connecting the light emittingdevice to the mount, wherein in an area underlying the small areacontact, the bonding structure comprises a plurality of metal regionsseparated by gaps, wherein nearest neighbor metal regions are separatedby a gap less than 5 microns wide.
 2. The structure of claim 1 whereinthe metal regions comprise gold bumps compressed by bonding the lightemitting device to the mount.
 3. The structure of claim 1 wherein themetal regions comprise a metal with a Young's modulus less than 150 GPa.4. The structure of claim 1 wherein in an area underlying the large areacontact, the bonding structure comprises a plurality of metal regionsseparated by gaps.
 5. The structure of claim 4 wherein the portion ofthe bonding structure underlying the large area contact is separatedfrom the portion of the bonding structure underlying the small areacontact by less than 40 microns.
 6. The structure of claim 1 wherein thesmall area contact comprises a center portion and an arm portion,wherein the arm portion extends from the center portion toward an edgeof the light emitting device, wherein a portion of the bonding structureunderlies the center portion and no portion of the bonding structureunderlies the arm portion.
 7. The structure of claim 6 furthercomprising a gap disposed between the mount and the arm portion.
 8. Thestructure of claim 6 wherein the small area contact is the metaln-contact, wherein the metal n-contact is formed in a trench formed inthe semiconductor structure, wherein a top surface of the metaln-contact is recessed relative to a top surface of the metal p-contact.9. The structure of claim 8 further comprising a dielectric layerdisposed between a portion of the metal p-contact and a portion of themetal n-contact, wherein a portion of a top surface of the dielectriclayer extends above the top surfaces of the metal n-contact and themetal p-contact.
 10. The structure of claim 9 further comprising aportion of the bonding structure disposed between the mount and theportion of the top surface of the dielectric layer extending above thetop surfaces of the metal n-contact and the metal p-contact.
 11. Thestructure of claim 6 wherein the center portion is no more than 45microns wide and the arm portion is no more than 25 microns wide. 12.The structure of claim 1 wherein no bonding structure is formed in asecond area underlying the large area contact, wherein the second areais aligned with a metal trace formed on the mount.
 13. The structure ofclaim 1 further comprising a continuous, linear metal bump disposedbetween the light emitting device and the mount proximate to an edge ofthe light emitting device, wherein the continuous, linear metal bumpforms a seal between the light emitting device and the mount.
 14. Thestructure of claim 1 further comprising a continuous, curved metal bumpdisposed between the light emitting device and the mount proximate to anedge of the light emitting device, wherein the continuous, curved metalbump forms a seal between the light emitting device and the mount. 15.The structure of claim 1 further comprising at least two lines of offsetmetal bumps disposed between the light emitting device and the mountproximate to an edge of the light emitting device, wherein the at leasttwo lines of metal bumps are arranged to collapse during bonding to forma continuous seal between the light emitting device and the mount.